Change all of body system to use entities and components (#2074)

* Early commit

* Early commit 2

* merging master broke my git

* does anyone even read these

* life is fleeting

* it just works

* this time passing integration tests

* Remove hashset yaml serialization for now

* You got a license for those nullables?

* No examine, no context menu, part and mechanism parenting and visibility

* Fix wrong brain sprite state

* Removing layers was a mistake

* just tear body system a new one and see if it still breathes

* Remove redundant code

* Add that comment back

* Separate damage and body, component states, stomach rework

* Add containers for body parts

* Bring layers back pls

* Fix parts magically changing color

* Reimplement sprite layer visibility

* Fix tests

* Add leg test

* Active legs is gone

Crab rave

* Merge fixes, rename DamageState to CurrentState

* Remove IShowContextMenu and ICanExamine

Content.Shared/GameObjects/ContentNetIDs.cs

@@ -63,7 +63,7 @@
         public const uint GAS_ANALYZER = 1057;
         public const uint DO_AFTER = 1058;
         public const uint RADIATION_PULSE = 1059;
-        public const uint BODY_MANAGER = 1060;
+        public const uint BODY = 1060;
         public const uint CLIMBING = 1061;
         public const uint BOLTACTION_BARREL = 1062;
         public const uint PUMP_BARREL = 1063;
@@ -77,6 +77,7 @@
         public const uint SLIP = 1071;
         public const uint SPACE_VILLAIN_ARCADE = 1072;
         public const uint BLOCKGAME_ARCADE = 1073;
+        public const uint BODY_PART = 1074;
 
         // Net IDs for integration tests.
         public const uint PREDICTION_TEST = 10001;